The fabrication of semiconductor devices on substrates typically requires the deposition of multiple metal, dielectric and semiconductive layers on the surface of substrates. These layers are typically deposited onto substrates in vacuum processing chambers. Some processing operations may require the deposition of additional layers while others may require the etching, or partial removal, of a previously deposited film layer.
One commonly used vacuum deposition process is physical vapor deposition (PVD), also referred to as sputtering. In a typical PVD process, a target comprised of the desired deposition material is exposed to a plasma and bombarded by ions from the plasma. This bombardment causes atoms or larger particles to be sputtered from the target and deposited on the substrate being processed. Typically in PVD processes, the geometry of the chamber and the spacing of the target from the substrate being processed is important in order to control the even distribution of the target material onto the substrate.
During processing, a substrate support member, often referred to as a pedestal, susceptor, or heater, is disposed in the processing chamber to support the substrate. A clamp ring is typically supported in the chamber above the support member on a shield. When a substrate is introduced into the chamber and supported on the support member, the support member and substrate are moved in the chamber relative to the clamp ring to pick up the clamp ring so that the clamp ring contacts the edge of the substrate and holds the substrate on the support member. As a result of the contact of the clamp ring with the edge of the substrate, the clamp ring shields the edge of the substrate from deposition material, thereby minimizing the usable area on the surface of the substrate.
Clamp rings have been provided having a seat portion which engages the top surface of the substrate and an overhanging roof portion which does not contact the top portion of the substrate. The purpose of the roof portion in some applications is to shield the edge of the substrate from deposition. The roof is typically spaced from the upper surface of the substrate to prevent deposition material from being deposited at points where the clamp ring contacts the substrate. If deposition material deposits at these contact points, the substrate can adhere to the clamp ring following deposition which can lead to other difficulties including particle generation or even system shut down to remove the substrate.
Clamp rings are generally formed as a continuous annular shaped member or an interrupted metal ring. As shown in FIG. 2, part of the ring 56 engages the substrate surface and exerts a downward force on the top, outer edge of the substrate 12 which is positioned on the support member. The weight of the clamp ring 30 holds the substrate in position for processing and assists in preventing substrate warpage. The fact that the clamp ring contacts the top surface of the substrate presents several problems. First, as previously mentioned, the clamp ring is likely to receive material deposits thereon as deposition processes are performed. This can cause adherence of the substrate to the clamp ring. Such adherence can hinder the removal of the substrate from the chamber following processing. Secondly, the clamp ring seat or contacting portion 56 shields a portion of the outer perimeter of the substrate surface. This reduces the useable surface area of the substrate on which electronic devices may be formed. This problem is generally referred to as edge exclusion.
Much effort has been directed at developing clamp rings that shield the edge of the substrate and control or prevent sticking of substrates to the clamp ring without the loss of excess usable surface area on the substrate. Typically, clamp rings adequately secure the substrate to the support member, but achieve this holding force at the expense of the outer perimeter of the substrate.
The trend in metallization is to provide as much coverage on the substrate surface as possible. This can be seen in full coverage deposition systems which do not utilize clamp rings or shadow rings during deposition. Further, the trend is to utilize copper as the material of choice in metallization and electroplating as the process of choice to deposit copper. However, copper deposited on the beveled edge of a substrate tends to flake or peel off during chemical mechanical polishing. As a result, edge exclusion has continued to be a requirement of some deposition schemes.
As shown in FIG. 2, one common approach to edge exclusion has involved extending the clamp ring across the gap between the edge of the substrate and the edge of the support member and forming a lip or seat extending over the edge of the substrate. Attempts to minimize loss of usable surface area have also required moving the inner terminus of the clamp ring lip which overhangs the edge of the substrate outwardly to more closely approach the edge of the substrate. To maintain a good aspect ratio (ratio of lip overhang width to height above the substrate) to minimize loss of usable surface area on the substrate has proven difficult. One successful approach in this regard is disclosed in U.S. Pat. No. 5,810,931 which is assigned to the assignee of the present invention and incorporated herein by reference.
Therefore, it would be desirable to provide a clamp ring which minimizes edge exclusion (maximizes die area) and also prevents copper (or other) metal deposition on the substrate backside and on the substrate bevel.